Highly Reversible Zn Metal Anode Stabilized by Dense and Anion‐Derived Passivation Layer Obtained from Concentrated Hybrid Aqueous Electrolyte

Abstract

Zinc metal is considered a promising anode material for aqueous zinc ion batteries. However, it suffers from dendrite growth, corrosion, and low coulombic efficiency (CE) during plating/stripping. Herein, a concentrated hybrid (4 m Zn(CF 3 SO 3 ) 2 + 2 m LiClO 4 ) aqueous electrolyte (CHAE) to overcome the challenges facing the Zn anode is reported. The developed electrolyte achieves dendrite-free Zn plating/stripping and obtains an excellent CE of ≈100%, surpassing the previously reported values. The combination of synchrotron-based in operando transmission X-ray microscopy, X-ray diffraction, and ex situ X-ray photoelectron spectroscopy analyses indicate that the denser, anion-derived passivation layer formed using the CHAE facilitates homogeneous current distribution and better prevents freshly deposited Zn from directly contacting the electrolyte than the looser, solvent-derived layers formed from a dilute hybrid aqueous electrolyte (DHAE). The beneficial effects of the CHAE on the compact, dense, and stable salt-anion-derived passivation layer can be attributed to its unique solvation structure, which suppresses the water-related side reactions and widens the electrochemical potential window. In the hybrid Zn||LiFePO 4 configuration, the CHAE-based cell delivered a stable performance of CE >99% and capacity retention >90% after 285 cycles. In contrast, the DHAE-based cell exhibits capacity retention of <65% after 170 cycles.

Highly reversible zinc metal anodes enabled by a three-dimensional silver host for aqueous batteries

“…The mass loading of LFP was controlled to be approximately 3 mg cm −2 (corresponding to a theoretical capacity of ∼0.5 mA h cm −2 ) and the capacity of Zn@a-Ag mesh was 2 mA h cm −2 . Thus, the negative-to-positive electrode capacity (N : P) ratio was fixed at 4 : 1 in our full cells, which is remarkably lower than the values reported in the literature, 52–58 where a thick Zn foil was always utilized as the anode. A low N : P ratio is necessary for the development of practical, high-energy-density Zn-based batteries.…”

“…Furthermore, unlike other cathode materials for Zn-based hybrid cells, 60,61 Zn 2+ ions cannot be inserted into FePO 4 during the discharging process, despite the fact that the radius of the Zn 2+ ion (0.74 Å) is slightly smaller than that of the Li + ion (0.76 Å). 55,57 The Nyquist plots in Fig. 5c and S14† demonstrate that Zn@a-Ag mesh//LFP possesses smaller charge transfer resistance than Zn//LFP, which should be attributed to the high conductivity of the Ag host.…”

“…Olivine LFP is a common cathode material for LIBs and can be paired with Zn anodes to prepare hybrid-ion batteries. 52–58 In contrast to conventional aqueous Zn-ion batteries, this type of aqueous battery operates through a dual-ion mechanism (Fig. S11†), which can avoid the sluggish Zn 2+ diffusion kinetics in the cathode materials and results in good rate performance.…”

Copper Nanoparticle-Modified Carbon Nanofiber for Seeded Zinc Deposition Enables Stable Zn Metal Anode

“…Meanwhile, the nucleation overpotentials on the bare Cu substrate using the CNFs-Zn anode were 33.0, 40.7, 42.3, 45.9, and 67.5 mV, respectively. This result indicates that the Cu@CNFs coating layer can effectively reduce the Zn deposition barrier . For Cu@CNFs-Zn||Cu cells, the average CE is higher than 98.8% over 100 cycles at 5 mA cm –2 (Figure S9a, blue).…”

“…This result indicates that the Cu@CNFs coating layer can effectively reduce the Zn deposition barrier. 54 For Cu@CNFs-Zn||Cu cells, the average CE is higher than 98.8% over 100 cycles at 5 mA cm −2 (Figure S9a, blue). Nonetheless, the CE of the Zn|| Cu cell deteriorated rapidly after 25 cycles due to the continuous formation of dead Zn and the growth of dendrites (Figure S9b, black).…”